Method and arrangement for controlling transmission oil temperature

ABSTRACT

A temperature control arrangement includes a heat exchanger which is fluidly connected via a transmission oil circuit to a transmission of the vehicle. A heat accumulator is fluidly connected to the transmission oil circuit and a control device is arranged in the transmission oil circuit. The control device subdivides the transmission oil circuit into an accumulator circuit containing the heat accumulator and a cooling circuit containing the heat exchanger. The heat accumulator alternately accumulates thermal energy from the transmission oil and delivers previously stored thermal energy to the transmission oil. The control device is configured to direct the transmission oil circulating within the transmission oil circuit at least partially to the heat exchanger and/or to the heat accumulator.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims foreign priority benefits under 35 U.S.C. §119(a)-(d) to DE 10 2013 221 367.0 filed Oct. 22, 2013, which is hereby incorporated by reference in its entirety

TECHNICAL FIELD

The present invention relates to a temperature control arrangement and corresponding method for transmission oil of a vehicle.

BACKGROUND

Transmissions form part of the drivetrain of a vehicle. In being arranged between engine and drive wheels, they serve to govern the ratio between engine speed and the respective rotational speed of the drive. In addition to single-speed or manual-shift multispeed transmissions, there are multispeed transmissions which also have automated operation. The types of automatic transmissions range from semiautomatic transmissions through automated and torque-converter automatic transmissions to continuously variable transmissions. Both manual and automatic transmissions may be combined, for example, with electric motors and/or internal combustion engines.

The individual components of transmissions are manufactured in such a way that they operate most efficiently within a given temperature range. As the temperature of the transmission rises in operation with increasing load and rotational speed, the transmission oil located therein must be cooled, special attention being paid to cooling in the case of automatic transmissions. For this purpose the transmission may be fluidly connected to an air/oil or to a water/oil heat exchanger. The water/oil heat exchanger serves to transfer heat between the coolant circuit of the internal combustion engine and the transmission oil, while the air/oil heat exchanger dissipates the thermal energy of the transmission oil to the ambient air.

Conversely, transmissions which are below said temperature range have increased friction which, in addition to increased wear, causes higher energy or fuel consumption. This has given rise to efforts to heat the transmission oil, and therefore the transmission itself, to an operating temperature as quickly as possible. As compared to internal combustion engines, however, transmissions need more time to heat up because combustion heat is lacking. Arrangements and methods for heating the transmission oil as quickly as possible are therefore known in the prior art. The heating is effected, for example, by using electric heaters or by a specified transfer of engine heat. The energy required for this purpose must ultimately be generated, for example, by the internal combustion engine.

For example, DE 41 04 093 A1 proposes a temperature control arrangement for a vehicle having an internal combustion engine. This arrangement comprises a main cooling circuit in the form of a first coolant circuit and a further, second coolant circuit. The first coolant circuit serves to fluidly connect the internal combustion engine to a heat exchanger. This is in the form of an air/coolant heat exchanger which is used to cool the coolant flowing through the internal combustion engine. By contrast, the second coolant circuit serves, inter alia, to fluidly connect an additional heat exchanger to an intermediate heat exchanger. In this case the additional heat exchanger is in the form of an air/coolant heat exchanger which serves to cool the coolant circulating in the second coolant circuit. By contrast, the intermediate heat exchanger is in the form of an oil/coolant heat exchanger, so that it serves to cool a transmission connected to the internal combustion engine. For this purpose, both coolant and transmission oil flow through the additional heat exchanger. A connecting line which fluidly links the two coolant circuits as required is further provided.

Because the first coolant circuit undergoes rapid heating, this heat can be supplied via the connecting line to the second coolant circuit as well. For this purpose there is provided, inter alia, a heat accumulator which, with its fluid-conducting connection to the first coolant circuit, can contribute to rapid heating thereof. In this way the thermal energy which can be supplied to the first coolant circuit by the heat accumulator, especially during a cold start, can be transferred onwards via the connecting line—although with a time offset—to the second coolant circuit. The thermal energy of the heat accumulator can thereby finally also be supplied, at least partially, to the additional heat exchanger for the transmission oil. The surplus thermal energy arising in the first coolant circuit can then be reused to charge the heat accumulator.

Because the heat exchanger of the transmission oil is connected to one of the coolant circuits, the transmission oil, and therefore the transmission itself, can be heated up only slowly. The causes of this are, in particular, the long distances and the many assemblies on the path between heat accumulator and transmission, which withdraw at least some of the thermal energy from the coolant. Furthermore, the heating of the whole system finally depends on the internal combustion engine, permitting only partially efficient operation with regard to heating the transmission.

For this reason it does not seem possible at present to achieve a more advantageous energy balance. For even if the internal combustion engine were not used as a direct or indirect source for the rapid heating of the transmission, additional electrical heat sources would be equally detrimental to the energy balance. The currently known temperature control arrangements and their operation therefore undoubtedly offer further scope for improvement

SUMMARY

Against this background it is the object of the invention to configure a temperature control arrangement for transmission oil of a vehicle and a correspondingly equipped vehicle, and a method for controlling the temperature of transmission oil of a vehicle, in such a way that, despite a specified use of an additional heat source, heating of the transmission oil which is more rapid and which improves the energy balance can be achieved.

It should be pointed out that the features and measures specified individually in the following description can be combined with one another in any desired technically useful manner and indicate further configurations of the invention.

A temperature control arrangement according to the invention for transmission oil of a vehicle, in particular for a manual transmission or an automatic transmission of a motor vehicle, is specified below. For this purpose the temperature control arrangement includes at least one heat exchanger. The heat exchanger is fluidly connected to a transmission of the vehicle via a transmission oil circuit. According to the invention, the temperature control arrangement further includes at least one heat accumulator. Said heat accumulator is fluidly connected to the transmission oil circuit. In this arrangement the heat accumulator is configured to accumulate, and therefore to store over a time period, at least a portion of thermal energy from the transmission oil. The heat accumulator is also configured to return thermal energy previously stored from the transmission oil at least partially to the transmission oil.

In addition, a control device is arranged in the transmission oil circuit. Said control device is configured to direct the transmission oil circulating inside the transmission oil circuit at least partially to the heat exchanger and/or to the heat accumulator. In this way the transmission oil can be supplied more or entirely to the heat exchanger, and more or entirely to the heat accumulator, as required. Thanks to the control device, therefore, the transmission oil is directed in a specified manner through the transmission oil circuit and, in particular, through the heat exchanger and the heat accumulator. In this process the particular control setting of the control device is based on the goals to be achieved: rapid heating of the transmission oil and/or efficient accumulation of the surplus thermal energy from the transmission oil.

The transmission oil circuit is subdivided by the control device into at least two circuits. In other words, the transmission oil circulating within the transmission oil circuit can be circulated in only one of these two circuits or, in partial amounts, in both simultaneously. Specifically, the transmission oil circuit may be subdivided into an accumulator circuit and a cooling circuit. In this case the heat exchanger and the heat accumulator are each arranged in a respective one of these two cooling circuits. Thus, the heat accumulator is arranged in the accumulator circuit of the transmission oil circuit while the heat exchanger is arranged in the cooling circuit of the transmission oil circuit.

Through the advantageous arrangement of the heat accumulator directly within the transmission oil circuit it is now possible to absorb the waste heat of the transmission via the transmission oil heated during operation of the transmission. In this respect, previous solutions have not provided for direct absorption of the thermal energy, which must be dissipated in any case. On the contrary, previous attempts have been made with the aim of extracting the surplus thermal energy from the transmission oil circuit as quickly as possible via the heat exchanger in order to achieve cooling of the transmission. Here, the invention actually turns to advantage at least a portion of the thermal energy, which would otherwise have to be dissipated, by storing it temporarily in the heat accumulator.

Because this thermal energy originates in the inherent operational heating-up of the transmission, which is required in any case, its withdrawal from the transmission oil circuit initially has no effect on the energy balance. On the contrary, the energy balance is sometimes significantly improved as soon as the thermal energy previously accumulated is returned to the transmission oil and therefore to the transmission. As a result, friction and therefore resistance within the transmission are reduced within a very short time, thereby reducing energy consumption and, in particular, fuel consumption.

Within the context of the invention, heat accumulators are understood to be assemblies which are able to absorb thermal energy and to release it as required. For example, the assembly may be, but is not limited to, a chemical heat accumulator.

Here, particular emphasis should be given to the arrangement according to the invention of the heat exchanger in the transmission oil circuit, which arrangement offers significant advantages in comparison to the arrangement in the regular cooling circuit of an internal combustion engine sometimes known.

A chemical heat accumulator admittedly has the general disadvantage of a low discharge rate. For this reason it initially seems less suitable for internal combustion engines or combustion engines. In comparison, the discharge rate of an “oil heat accumulator” can be significantly higher if the hot oil is fed, for example directly, into the engine oil circuit. However, chemical heat accumulators discharge the stored energy via a chemical reaction, which energy can then be dissipated to the oil. This discharge rate, for a heat accumulator of a size which can be used appropriately in a motor vehicle, is therefore typically lower than that of the oil heat accumulator. On the other hand, the stored thermal energy can be regarded as approximately equal for a both systems, for a chemical heat accumulator and for an oil heat accumulator. In a possible configuration, therefore, a chemical heat accumulator may be advantageously usable for a transmission since, firstly, the thermal mass of a transmission is less than that of an internal combustion engine and, secondly, warm-up of the engine usually takes significantly longer than that of the transmission.

Thus, because of the usually relatively low thermal energy of an appropriate heat accumulator in comparison to the warm-up energy needed for an internal combustion engine, only small temperature increases are to be expected. Against this background, the heating of a transmission is significantly more advantageous than that of an internal combustion engine, since a transmission has lower thermal inertia compared to an internal combustion engine, or combustion engine. This therefore leads to a significantly greater temperature increase of the transmission in comparison to an internal combustion engine. Only in this way can a substantial saving of energy, and in particular of fuel, be achieved in a cold start. The heat accumulator may therefore be in the form of a chemical heat accumulator. Self-evidently, the heat accumulator may also be in the form of an oil heat accumulator.

Especially preferably, the control device comprises at least one valve or a valve arrangement by which the guidance of the transmission oil with regard to its direction and path within the transmission oil circuit can be controlled. For this purpose the valve or valve arrangement has at least one control position which either allows or does not allow the transmission oil to flow through the heat accumulator. At least two control positions are preferably provided, the transmission oil being directed through the heat exchanger in one control position and to the heat accumulator in the other, depending on the temperature of the transmission oil in each case.

Thus, transmission oil which is below the operating temperature of the transmission and therefore can be designated cold can preferably be conducted not through the heat exchanger but to the heat accumulator before entering the transmission. In this way it absorbs previously accumulated thermal energy from the heat accumulator, which it then transfers at least partially within the transmission to individual components thereof.

By contrast, the transmission oil which is above the operating temperature of the transmission and is therefore to be designated hot is preferably conducted to the heat accumulator. In this case it can be conducted through the heat exchanger either before or after passing through the heat accumulator, before it is returned to the transmission. In this way the hot transmission oil is cooled, especially by the heat exchanger but also by the heat accumulator which, of course, also withdraws thermal energy from the transmission oil. The transmission oil cooled down in this way can then again absorb thermal energy from the components of the transmission as it passes into the transmission, whereby these components, and therefore the transmission as a whole, are cooled.

The invention provides for an advantageous arrangement of the control device, which may preferably be located upstream of the heat exchanger. In this case the portion of the transmission oil leaving the transmission first passes through the control device, which predefines the subsequent path of the transmission oil. Depending on the temperature of the transmission oil, it can be conducted either to the heat exchanger or to the heat accumulator or to both elements.

The heat accumulator should preferably be designed such that the power for charging the heat accumulator matches the cooling capacity of the heat exchanger. In this way, the charging of the accumulator would have little or no effect on the transmission oil temperature. The control by the control device would thereby be considerably simplified.

In principle, therefore, intermediate positions for the control device are possible, so that the transmission oil can be conducted simultaneously both through the heat exchanger and to the heat accumulator. The respective through-flow quantities can also be controlled by the control device in order to obtain a regulation of the circulating transmission oil as optimal as possible.

In a development of the invention, it is envisaged that the heat exchanger used to cool the transmission oil may be configured as an air/oil heat exchanger. In this way, no further systems are stressed by the waste heat of the transmission oil. The surplus thermal energy of the transmission oil can thereby be dissipated—if not to the heat accumulator—to the atmosphere.

The temperature control arrangement according to the invention as specified hereinbefore makes it possible to achieve an improved energy balance despite an additional heat source for the transmission oil in the form of the heat accumulator. Because the thermal energy to be accumulated is absorbed and accumulated from the transmission oil almost exactly at the location where it arises, the heat accumulator can already reach maximum charge after a short operation of the vehicle. Furthermore, the direct proximity of the heat accumulator to the transmission makes possible rapid or at least assisting heating-up to operating temperature, since the transmission oil preferably absorbs thermal energy from the heat accumulator shortly before entering the transmission. Since the heat generated during operation of the transmission must in any case be dissipated upon exceeding a given temperature, this heat can therefore advantageously be utilized, to an extent, with a time offset. Depending on the configuration of the heat exchanger, therefore, sufficient energy is available even during a cold start to bring the transmission oil, and therefore the transmission itself, as quickly as possible to operating temperature during operation thereof.

It should further be mentioned that, of course, the heat accumulator must be charged so that it is able, at all, to absorb, and therefore store, the heat of the transmission oil. For this purpose the hot transmission oil is supplied to the heat accumulator, which can be effected by appropriate activation of the control device. In this case the heat exchanger can be bypassed in the cooling circuit of the transmission oil circuit, so that practically uncooled transmission oil reaches the heat accumulator. In this case it can usefully be provided that the heat accumulator, in an ideal configuration, has the same capacity for storing the heat as the capacity of the heat exchanger for cooling the transmission oil. In other words, the transmission oil is to an extent cooled in the heat accumulator (as already mentioned) when the heat accumulator has to be charged. It is thus assured at the same time that the transmission oil temperature does not become too high when charging the heat accumulator. Once the heat accumulator is charged, the control device is activated appropriately, so that the transmission oil is again directed to the heat exchanger.

The invention is also directed at a vehicle which, in addition to a drive motor and a transmission coupled torque-transmittingly thereto, has a temperature control arrangement for the transmission oil of the transmission. The temperature control arrangement may be, in particular, a temperature control arrangement as previously specified. The drive motor may be, for example, electrically powered. However, the drive motor may also be, for example, an internal combustion engine.

The invention is further directed at a method for controlling the temperature of transmission oil of a vehicle, in particular a motor vehicle, the temperature control being effected via a suitable temperature control arrangement. This temperature control arrangement may be, in particular, the temperature control arrangement previously specified.

For this purpose the transmission oil, in order to be cooled, is conducted through a transmission oil circuit fluidly connected to a transmission and to a heat exchanger. According to the invention, the transmission oil is conducted to a heat accumulator before or after passing through the heat exchanger. It is thereby made possible that at least a portion of the thermal energy is withdrawn from the transmission oil and can initially be accumulated in the heat accumulator.

A control device arranged in the transmission oil circuit is further provided. The control device is configured such that the transmission oil can be conducted at least partially to the heat exchanger and/or to the heat accumulator, depending on its temperature.

The transmission oil circuit is subdivided by the control device into an accumulator circuit and a cooling circuit. In this way, depending on the particular control position of the control device, at least a proportion of the transmission oil can be conducted through the accumulator circuit and/or through the cooling circuit.

The advantages resulting therefrom have already been set forth in detail in connection with the temperature control arrangement according to the invention previously explained, so that reference is made here to the preceding discussion. Moreover, this also applies to the further advantageous configurations of the method according to the invention to be explained hereinafter, and to the vehicle previously specified having such a temperature control arrangement.

In an advantageous development, it is provided that the transmission oil, in order to be heated, can be conducted first to the heat accumulator and then to the transmission. In this way at least a part of the thermal energy previously accumulated in the heat accumulator can be delivered back to the transmission oil.

Further advantageous details and effects of the invention are explained in more detail below with reference to an exemplary embodiment represented in the following Figures, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic structure of a temperature control arrangement according to the invention,

FIG. 2 shows the temperature control arrangement in a first control position, and

FIG. 3 shows the temperature control arrangement in a second control position.

DETAILED DESCRIPTION

As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

In the different figures, identical parts are denoted by the same reference symbols so that, as a rule, they are described only once.

FIG. 1 shows a temperature control arrangement 1 according to the invention in a schematic representation. The temperature control arrangement 1 serves to control the temperature of transmission oil 2 of a vehicle (not shown in detail). For this purpose the temperature control arrangement 1 includes a heat exchanger 3. A transmission 4 of the vehicle (not shown), which is fluidly connected to the heat exchanger 3 by a transmission oil circuit 5, can further be seen.

With reference to the representation in FIG. 1, a heat accumulator 6 fluidly connected to the transmission oil circuit 5 is arranged on the right. A control device 7 which is arranged in the transmission oil circuit 5 upstream of the heat exchanger 3 can further be seen.

The control device 7 is configured to conduct the transmission oil 2 circulating inside the transmission oil circuit 5 at least partially to the heat exchanger 3 and/or to the heat accumulator 6, as is further clarified below:

FIG. 2 shows a first control position A of the control device 7. In this case the transmission oil circuit 5 is reduced to an accumulator circuit 8. In the present example the accumulator circuit 8 is marked by continuous lines while the remaining conduits of the transmission oil circuit 5 are indicated by broken lines. As can be seen, in the first control position A the transmission oil 2 flows through the accumulator circuit 8 in such a way that the transmission oil 2 from the transmission 4 is conducted first to the control device 7 and then directly to the heat accumulator 6.

Because the heat accumulator 6 is configured to deliver at least a portion of thermal energy previously stored from the transmission oil 2 at least partially to the transmission oil 2, the transmission oil 2 is heated as it passes through the heat accumulator 6, before returning to the transmission 4. In this way the heating of the transmission is at least assisted, and in particular accelerated.

FIG. 3 shows a second control position B of the control device 7. This position is adopted when the transmission oil exceeds a predetermined temperature. For this purpose a temperature sensor (not shown in detail) may, for example, be arranged in the transmission oil circuit, in order to supply the control device with information on the temperature of the transmission oil or to control its control positions A, B. In the second control position B the transmission oil circuit 5 is reduced to a cooling circuit 9.

In the present example the cooling circuit 9 is marked by continuous lines, while the remaining conduits of the transmission oil circuit 5 are indicated by broken lines. As can be seen, in the second control position B the transmission oil 2 flows through the cooling circuit 9 in such a way that the transmission oil 2 from the transmission 4 is conducted directly to the heat exchanger 3. The heat exchanger 3 is in the form of an air/oil heat exchanger, so that the surplus thermal energy from the transmission oil 2 can be dissipated to the ambient air via the heat exchanger 3. After passing through the heat exchanger 3, the transmission oil 2 is then conducted directly back to the transmission 4, bypassing the heat accumulator 6. Here, cooling of the transmission oil 2 is taking place primarily, the heat accumulator 6 being already fully charged.

FIG. 1, already explained in detail, consequently shows a mixed form of both the first and second control positions A, B of the control device 7 shown in FIGS. 2 and 3, and the associated circuits in the form of the accumulator circuit 8 and the cooling circuit 9. Here, the transmission oil 2 has already reached a temperature which makes its cooling necessary; for this purpose the control device 7 has been moved to a third control position C, in which the transmission oil 2 is conducted both through the heat exchanger 3 and to the heat accumulator 6. As this happens the transmission oil 2 is cooled by the heat exchanger 3 but also by the heat accumulator 6, which withdraws and accumulates thermal energy from the transmission oil 2.

In addition, the configuration according to FIG. 2 can be used to charge the heat accumulator 6 if the transmission oil has the corresponding temperature. In this case it is favorable if the heat accumulator 6 has the same capacity as the heat exchanger 3, so that the transmission oil is to some extent cooled in the heat accumulator 6. This operating position can therefore be used, on the one hand, to heat the transmission oil from the heat accumulator 6, so that the warm-up phase is reduced. On the other hand, the operating position according to FIG. 2 can be used to charge the heat accumulator 6. However, once the heat accumulator is sufficiently charged, the control device 7 should be activated to allow transmission oil to flow through the heat exchanger 3 again. The operating position according to FIG. 2 is therefore provided both to heat the transmission oil, for example in a warm-up phase of an internal combustion engine, and to “charge” the heat accumulator 6 only temporarily, that is, from time to time for a very short period.

While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention. 

What is claimed is:
 1. A temperature control arrangement for transmission oil of a vehicle, comprising: a heat exchanger fluidly connected to a transmission oil circuit of the transmission of the vehicle and configured to conduct thermal energy from the transmission oil to ambient air; a heat accumulator fluidly connected to the transmission oil circuit and configured to alternately absorb thermal energy from the transmission oil and to deliver previously stored thermal energy to the transmission oil; and a control device arranged in the transmission oil circuit by which the transmission oil circuit is subdivided into an accumulator circuit containing the heat accumulator and a cooling circuit containing the heat exchanger, the control device configured to alternately direct the transmission oil circulating within the transmission oil circuit to the cooling circuit and to the accumulator circuit.
 2. The temperature control arrangement of claim 1, wherein the control device is configured to direct transmission oil through the heat accumulator in response to an oil temperature being less than a threshold and to direct transmission oil through the heat exchanger in response to the oil temperature being greater than the threshold.
 3. The temperature control arrangement of claim 1, wherein the control device is arranged upstream of the heat exchanger.
 4. The temperature control arrangement of claim 3, wherein the accumulator circuit and cooling circuit are arranged in parallel.
 5. The temperature control arrangement of claim 1 wherein the heat accumulator is a chemical heat accumulator.
 6. A temperature control arrangement comprising: a heat exchanger; a chemical heat accumulator; and a control device configured to direct transmission oil through the heat accumulator in response to a temperature of the transmission oil being less than a threshold and to direct the transmission oil through the heat exchanger in response to the temperature exceeding the threshold.
 7. The temperature control arrangement of claim 6, wherein the control device is arranged upstream of the heat exchanger.
 8. The temperature control arrangement of claim 7, wherein the heat accumulator and the heat exchanger are arranged in parallel.
 9. The temperature control arrangement of claim 6 wherein the heat exchanger is an oil to air heat exchanger.
 10. A method of controlling a temperature of transmission oil comprising: directing the transmission oil through a heat accumulator such that thermal energy from the transmission oil is absorbed in the heat accumulator; directing the transmission oil through an oil to air heat exchanger such that the oil is cooled; and directing the transmission oil through the heat accumulator such that the thermal energy previously absorbed in the heat accumulator is delivered to the transmission oil.
 11. The method of claim 10 wherein, in response to the transmission oil temperature being less than a threshold, the transmission oil is directed through the heat accumulator but not through the heat exchanger.
 12. The method of claim 11 wherein, in response to the transmission oil temperature being greater than the threshold, directing a portion of transmission oil flow through the heat accumulator and simultaneously directing a remainder of transmission oil flow through the heat exchanger.
 13. The method of claim 11 wherein, in response to the transmission oil temperature being greater than the threshold, the transmission oil is intermittently directed through the heat accumulator to charge the heat accumulator. 